alt Hacker NewsYou can find random PDP, VAX, even X86 systems that have lifespans 20+ years. As for a single boot probably a much smaller corpus, maybe some forgotten Sun SPARC in a telco on -48V DC power bus.
A VAXCluster or Sysplex(S/390) would I guess be more analogous but those can be a bit Ship of Theseus since you can change the hardware out over time.
For VMSClusters 8 to 10 years seems to be a pretty common uptime for long lived clusters. I worked a gig a few years ago that had a VMSCluster that was up for 19 years at that point. Started on alpha, migrated to itanium, then I helped migrate it to x86. It was the oldest I've personally seen, though I have heard legends of much older.
My current contract has a PDP-11/70 running RSX-11 that's been up since 1992. It's uptime is longer than mine! Poor thing is getting retired next year though.